Method of producing refractory metals



United S t s ater Mnrnon on rnonucnso REFRACTORY METALS 1, Application January 3, 1955, Serial No. 479,483

' I 4 Claims. (Cl.7584.5)

This invention relates to the production of metals and more particularly to .the production of refractory metals suchastitanium and the like. In the previous application-of Keller et al., Serial No. 434,648, filed June 4, 1954, now Patent No. 2,846,304, granted August 5, 1958, there is described a process for the production of titanium in which high yields of large crystals of titanium are obtained by the two-stage reduction of a titanium halide. It is va principal object of the present invention to'provide an improved apparatus and process particularly adapted for utilization with the invention described in the above Keller et a1. application.

Another object of the invention is to provide an improved process for localizing the production of refractory metal crystals.

' Still another object of the invention is to provide an improved apparatus for operation of a process of the above type. i 7

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and the order of one or more of such steps with respect to each of the others, and the apparatus possessing the construction, combination of elements and arrangement ofparts which are exemplified in the following detailed disclosure, and the scope of the application. of which will be indicated in-the claims. 1

For a fuller understanding of the natureand objects of the invention, reference should be had to the following-detailed description taken in connection with the accompanying drawing.

In'the present invention, the' refractory metal compound is dissolved in a fused salt and is reduced to the refractory 'metal'in the form of relatively large crystals by means of a liquid metal reducingagent. In a preferred embodiment of the invention, the refractory metal I, I

compound is a titanium halide'so that titanium crystals are'the end product. The present' invention also preferablyincludes atwo-stage reduction of the titanium halide to first produce a solution of titanium lower halides in a fused salt; such 'as sodium chloride. 7 halide dissolved in the molten salt is then preferably reduced to metallic titanium by means of 'a reducing agenr'which is sprayed across the surface of the solutipnj 'lhis"reducing agent'is preferably sodium, and

The titanium the invention will be described iii-connection with the utilization of sodium as the reducing agent, titanium lower chlorides as the titanium halide, and sodium chloride as the fused'salt.

' The present invention is particularly directed to improvements in apparatus and techniques for accomplishing the second stagereduction. As pointed out in the 'Keller'etal. applicationfSerial No. 434,648, it is highly ,desirable" to so conduct the second stage reduction that sodium is uniformly sprayed across the surface of a solution oftitanium dichloride infused sodiuruchloride. 1 As a result of this spraying, a crust of fine particles of Patented Dec. 1, 1959 of a suitable grid or the like, this grid being helpful in preventing collapse of the crust in later stages of the titanium crystal growth. As more sodium is fed to the salt bath, the level of the salt tends to rise above the crust due to the formation of more sodium chloride. During this further feed of sodium, titaniumcrystals grow from the bottom of the crust to form an interlaced mass of relatively large titanium crystals, many of-which have dimensions on the order of an inch or so. When it is desired to remove the product titanium from the reactor, it has been found that, in many cases, some of the titanium is quite firmly fastenedto the walls of the reactor. It is necessary to chip this titanium'from these walls, a fairly time-consuming and relatively expensive operation. .In the present invention, adhesion of the product titanium to the reactor wall is substantially prevented by isolating and localizing the titanium crystal growth. This is accomplished in a preferred embodiment by feeding thesodium 'to a limited portion of the bath containing the dissolved dichloride and isolating this limited portion'o'f the bath, particularly at the surface, from the remainder of the bath. The space above the limited portion is also preferably isolated from the space above the remainder of the bath so as to prevent migration of sodium vapors from the point of feed to the other portions of the bath; Additionally, the means for isolating the point of sodium feed from. the remainder of the bath is electrically insulated from the main walls of the reaction chamber. Accordingly, any flow of electrons from the point of sodium feed to the point of minimum sodium concentration adjacent the reactor walls is substantially prevented.

Referring now to the drawing, there is illustrated one method of practicing the invention wherein 10 represents a reactor containing a charge of fused salt 12, this fused salt preferably comprising sodium chloride and containing a dissolved mixture of titanium dichloride and ti-.

tanium trichloride. Positioned within the fused salt is a cylinder 13, this. cylinder 13 preferably comprising nickel, titanium or the like and extending upwardly into space 14 above the fused salt 12. The upper end of cylinder 13 is supported by a flange 15 so that space 14:: above the interior of the cylinder 13 is isolated from the remainder of the space 14. The reactor also 'in cludes a cover 16, a plurality of insulating gaskets 18, and clamps 20 for holding the cover on the reactor 10 and also for positioning the cylinder 13. Sodium is preferably fed through a pipe 21 to the space 14a, being distributed by-means of a spinning disc 22 of the type described in the copending application of Hellier, Serial No. 442,525, filed July 12, 1954, now abandoned.- If desired, titanium crust supports 23 may be provided within cylinder 13.

The pressure in the space 14a is preferably maintained equal to that in the space 14, although the pressureequalizing means is so arranged as to prevent transfer of sodium vapors from the space 1411 to space 14. This pressure-equalizing means, in a preferred embodiment, comprises a tube 24, a sodium condenser 26, and

315,461, Equally, titanium trichloride can be made by the tech- V 2,915,383 v, n l

ing (not shown). Sodium is then fed at a relatively slow rate, for example, on the order of 2 pounds per hour per square foot of molten sodium chloride surface. The sodium is preferably sprayed uniformly across the surface of the salt bath i'nsicl'e'of cylinder 13 so as to initially form a titanium crust; as described in the above mentioned Keller et al. application Serial No. 434,648, this crust being supported by supports 23. of sodium provides for dissolution of sodium in a laycn of relatively pure sodium chloride which is localized by the crust. Simultaneously, titanium crystals commence growing from the underside of the titanium crust and from both sides of cylinder 13. Since cylinder 13 is electrically insulated from the reactor walls, electrons do not travel to the wall and titanium crystal growth will not start outwardly from the reactor Walls. Accordingly, titanium crystal growth is localized on the cylinder13. When the reaction has been substantially completed, cylinder 13 can be removed from the residual salt, carrying therewith amass of titanium crystals adhering thereto. If desired, additional supports for the titanium crystals can be provided on the interior and exterior surfaces of cylinder l13. Additionally, holes may be provided in cylinder 13, below the surface of the bath, to assist in providing return paths for the chloride ions.

While only one cylinder 13 has been shown, numerous other cylinders may be provided. Equally, many shapes other than cylinders may be employed for isolating the limited portions to which sodium is'fed. other, types of insulation may be.provided on the insulating gaskets. 18 illustrated. Frozen salt maybe employed or ceramics when the temperature is such that reaction between the insulator and the sodium or other vapors is not a problem. the type described in the copending application of Vaughan, Serial No. 478,652, filed December 30, 1954, can be employed. Equally, feed of sodium below the surface can be accomplished as described in the co- Further feed Additionally, I

If desired, a titanium crust breaker of pending application of Keller et al., Serial No. 470,453, J

14 and 14a, it should be apparent that a predetermined difference in pressure may be maintained in these two spaces. Thus one space may have a. higher inert gas pressure than the other space. Many other means of equalizing these pressures can also be employed.

Numerous alternative methods of practicing the present invention may be employed. For example, the temperature of the reaction mass may be widely varied from slightly above the melting point of the salt to temperatures on the order of 1000 C. and above. Numerous reducing agents other than the sodium can be employed, for example, potassium, calcium, magnesium, lithium and various combinations of these elements'may be utilized. From the standpoint of cheapness, sodium, sodium-potassium alloy or magnesium are preferred.

Other halides of titanium may be'utilized, although,

from the standpoint of cost, ease of handling, etc., the tetrachloride is preferred.

Additionally, the reactor can be fed with lower halides of titanium such as titanium trichloride manufactured from titanium-bearing materials in the manner shown in the copending applications of Singleton, Serial. No. 304,- 388, filed August 14, 1952, now Patent No. 2,770,541, granted November 13, 1956, and Singleton, Serial No. filed October 18, 1952, now abandoned.

nique described by Sherfey et al., Journalof Research of the Bureau of Standards, 46, 299-300, April 1951. Additionally, the dichloride of titanium can be manufactured by numerous processes such as disproportionation of the trichloride or partial reduction of the trichloride or tetrachloride.

' The present invention can be equally employed for the manufacture of titanium alloys by the coreduction of the chlorides, for example, of zirconium, vanadium, chromium, manganese, iron, nickel, cobalt, columbium, tantalum, molybdenum, tungsten or silicon. The alloy may be a binary alloy or it may be an alloy containing three or four constituents. loys, the same general conditions of the reduction of the titanium halide and reducible compounds of the alloy ing constituents must be employed. Accordingly, when used in the claims, the word titanium is intended to mean alloys thereof as well as the pure metal.

While the invention has been particularly described in connection with the production of titanium, it is also applicable to the production of other refractory metals such as zirconium, thorium, vanadium, columbium, tungsten, tantalum, molybdenum and the like by the reduction of reducible compounds such as the halides of such refractory metals dissolved in suitablenfusedwsalts. It should be additionally pointed out. that thesaltlmixture in which the reduction is carried out maybeformedof numerous halides which canbe mixed halides, single halides and halides of materials other than the specific reducing agent or agents employed in the reaction. From the standpoint of simplicity, offoperationand ease of control, however, it is preferred that the .salt be the chloride of the reducing" agent... It is quite feasibleto employ binary'and ternary mixtures of. halides having quite low melting points.

It should be pointed out, in connection with a consid: eration of the varioussalts which. can be. employed, that these salts should be completely anhydrous. and free of any contaminants such as carbon, nitrogen, oxygen or hydrogen. This is particularly true when making metals such as titanium due to the. tremendous reactivity of titanium metal at temperatures on the order of 800 C. to 900 C. and above.

In the above specification, reference. has been made particularly to the preferred titanium chlorides, tetrachloride and dichloride. In most instances, the trichloride is equally useful and, as a matter of fact, it. is extremely unlikely that any system having an appreciable concentration of one of the lower chlorides: of titanium will not have at least some of the other lower chloride also present. It should be apparent that one can, also employ the corresponding di-, tri-, and tetrahalides from the group consisting of the iodides, bromides and fluorides of titanium, a 1

Since certain changes may be made in the above process and apparatus without departing. from the scope, of the invention herein involved, it is intended that all mattercontained in the above description, or shown in the accompanying drawing, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. In a process formanufacturing a refractory metal selected from the group consisting of zirconium, thorium,

vanadium, columbium, tungsten, tantalum, andmolybdenum where a halide of the refractory metal dissolved halides, the improvement which comprises confiningthe fused salt bath in a metal-walled reactor, addingzmolten reducing agent to a limited portionof the fused salt bath,

preventing passage of reducingvapors from the limited portion to the space above the remainder. of the bath by means of a vapor barrier, equalizingthe gas pressures existing above the limited portion and the remainderof the bath, and electrically insulating thejmetal reaction chamber walls from the vapor herein.

t 2. In a process for producing titanium wherein a lower In. the manufacture of alhalide of titanium is dissolved in a fused salt bath and is reduced to titanium crystals by means of a metallic reducing agent selected from the class consisting of reducing agent to a limited portion of the fused salt bath,

preventing passage of reducing agent vapors from the limited portion to the space above theremainder of the bath by means of a vapor barrier, equalizing the gas pressures existing above the limited portion and the remainder of the bath, and electrically insulating the'metal reaction chamber walls from the vapor barrier.

3. In a process for producing titanium wherein a lower halide of titanium is dissolved in a fused salt bath and is reduced to titanium crystals by means of a metallic reducing agent selected from the class consisting of the alkali metals and the alkaline earth metals, the molten salt comprising a halide selected from the group consisting of the alkali metal halides and the alkaline earth metal halides, the improvement which comprises confining the fused salt bath in a metal-walled reactor, adding molten reducing agent to a limited portion of the fused salt bath, preventing passage of reducing agent vapors from the limited portion to the space above the remainder of the bath by means of a vapor barrier, and electrically insulating the metal reaction chamber walls from the vapor barrier.

4. The process of claim 2 wherein the titanium lower halide is a titanium lower chloride and the reducing agent comprises sodium.

References Cited in the file of this patent UNITED STATES PATENTS 452,030 Castner May 12, 1891 2,478,594 Queneau Aug. 9, 1949 2,586,134 Winter Feb. 19, 1952 2,607,674 Winter Aug. 19, 1952 2,621,121 Winter Dec. 9, 1952 2,647,826 Jordan Aug. 4, 1953 2,739,115 Gall et al. Mar. 20, 1956 2,783,192 Dean Feb. 26, 1957 OTHER REFERENCES Handbook of Chemistry and Physics, 26th edition, 1942, pages 402, 403, 450, 451, 476 and 477.

Journal of Metals, April 1950, pages 634-640. 

3. IN A PROCESS FOR PRODUCING TITANIUM WHEREIN A LOWER HALIDE OF TITANIUM IS DISSOLVED IN A FUSED SALT BATH AND IS REDUCED TO TITANIUM CRYSTALS BY MEANS OF A METALLIC REDUCING AGENT SELECTED FROM THE CLASS CONSISTING OF THE ALKALI METALS AND THE ALKALINE EARTH METALS, THE MOLTEN SALT COMPRISING A HALIDE SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METAL HALIDES AND THE ALKALINE EARTH METAL HALIDES, THE IMPROVEMENT WHICH COMPRISES CONFINING THE FUSED SALT BATH IN A METAL-WALLED REACTOR, ADDING MOLTEN REDUCING AGENT TO A LIMITED PORTION OF THE FUSED SALT BATH, PREVENTING PASSAGE OF REDUCING AGENT VAPORS FROM THE LIMITED PORTION TO THE SPACE ABOVE THE REMAINDER OF THE BATH BY MEANS OF A VAPOR BARRIER, AND ELECTRICALLY INSULATING THE METAL REACTION CHAMBER WALLS FROM THE VAPOR BARRIER. 